One goal of this project is to better understand the mechanisms of the ionic conductance in membranes which are voltage-dependent and excitable. Another goal is to determine how drugs influence these channels. These studies involve the use of the squid giant axon and the giant barnacle muscle fiber. We have continued studies on the mechanism of drug-channel interactions in the squid giant axon membrane. In particular, we have studied yohimbine, phenytoin, and perhexiline, and found that all three exhibit voltage-dependent behavior. We have also studied different types of oscillatory behavior in the barnacle muscle fiber, and developed a mathematical model to explain the behavior. The model is based on experimentally-determined properties of potassium channels and calcium channels.